Rapid weight loss, reduced muscle mass

If you lose weight too fast, lose more muscle when you lose weight more slowly, a new study shows.

The researchers assigned 25 participants to a diet of five weeks very low in calories, with just 500 calories a day. Another 22 volunteers underwent 12 weeks a diet low in calories, with 1,250 calories a day.

 The findings were presented Wednesday at the European Congress on Obesity in Bulgaria.

The researchers found that right after finishing diets, both groups had similar levels of weight loss. The average weight loss was just over 19 pounds (8.6 kilos) between the very low calorie diet, and just under 19 pounds between those who made the low calorie diet.

The researchers then observed the loss of fat-free mass, which includes all body tissues except fat. The important tissues are blood, bones, organs and muscles. But the mass of organs, blood and bones does not change during dieting. Therefore, changes in fat-free mass during diets are mainly due to changes in muscle mass.

Participants in the very low calorie diet lost about 3.5 pounds (1.6 kilos) of fat-free mass, and those who made the low calorie diet, 1.3 pounds (0.60 kilos). The fat-free mass formed 18 percent of weight loss in the group of the very low calorie diet, and 7.7 percent weight loss in the group of low calorie diet, the study found.

Four weeks after finishing diets, reductions in fat-free mass were on average 1.8 pounds (0.8 kilos) in the group of very low calorie diet, and 0.7 pounds (0.3 kilos) in the group the low calorie diet. The fat-free mass formed 9.4 percent of weight loss in the group of the very low calorie diet, and 2.9 percent weight loss in the group of low-calorie diet, according to the report.

"The loss of fat-free mass was even greater after weight loss induced by rapid diet in slow, with a total weight loss like" the authors of the study, Roel Vink and Marleen van Baak concluded, the Faculty of Nutrition, Toxicology and Metabolism, Maastricht University, and colleagues.

However, the study authors also noted in a press release of the meeting that muscle loss among people on very low calorie diet probably overestimated immediately after finishing the diet, compared to four weeks later.

This is probably because they had a greater loss of water and glycogen (a natural form of sugar in the body) when right diet had just completed four weeks later, the researchers explained.

Research presented at meetings should be viewed as preliminary until published in a peer-reviewed medical journal.